The present invention relates to a stretchable adhesive nonwoven fabric having an excellent adhesive strength as well as air permeability and flexibility.
A hot-melt nonwoven fabric is used to laminate the nonwoven fabric with the adherend, and fuse the nonwoven fabric with heating to bond it. As the hot-melt nonwoven fabric, those made of a resin such as ethylene-vinyl acetate copolymer (EVA), polyethylene-atactic polypropylene (APP), ethylene-ethyl acrylate copolymer (EEA), polyamide, polyester or the like has hitherto been known.
The resin constituting the hot-melt nonwoven fabric is incorporated with plasticizers, tackifiers and waxes, and is put into practice to improve various performances which are generally required for use as an adhesive material. However, such a nonwoven fabric is poor in chemical resistance, thermal resistance, cleaning resistance and flexibility causing impairment of laminates to cause a problem that the pleasant feel to the touch of the laminate is drastically impaired.
As a method of solving these problems, for example, a method of forming a thermoplastic polyurethane resin into a film and using the film as an adhesive material has been disclosed in Unexamined Patent Publication (Kokai) Nos. 7-97560 and 9-221640.
However, the film made of the thermoplastic polyurethane resin causes a problem air permeability of the laminate is drastically lowered or completely lost.
An object of the present invention is to solve these problems of previously known arts and provide a stretchable adhesive nonwoven fabric, which is rich in flexibility and is excellent in adhesive properties and air permeability.
The present inventors have intensely studied to solve these previous problems. As a result, they have made an invention relating to a stretchable adhesive nonwoven fabric prepared by laminating continuous filaments made of a thermoplastic polyurethane resin, which comprises an aliphatic diisocyanate and/or an aromatic diisocyanate, a polymeric diol and a chain-extending agent and has a hardness (JIS-A hardness) of 65 to 98 degrees and a flow initiating temperature within a range from 80 to 150xc2x0 C., into a sheet, and fusion-bonding the filaments themselves with their own heat at the contact point of the laminated filaments thereby to form fibers.
The aliphatic diisocyanate used in the present invention is preferably an aliphatic diisocyanate having 4 to 13 carbon atoms. Examples thereof include straight-chain diisocyanates such as 1,4-tetramethylene diisocyanate, 1,5,-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,8-octamethylene diisocyanate and isophorone diisocyanate; and alicyclic diisocyanates such as cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, hydrogenated xylene diisocyanate, norbornane-diisocyanate methyl. An aliphatic diisocyanate having a methyl side chain in a molecule, for example, trimethyl-hexamethylene diisocyanate, methylbutane diisocyanate, methylpentane diisocyanate or the like is also preferably used.
They can be used alone or in combination with the above diisocyanates having no side chain.
Examples of the aromatic diisocyanate used in the present invention include 2,4-torilene diisocyanate, 4,4xe2x80x2-diphenylmethane diisocyanate, xylylene diisocyanate, phenylene diisocyanate, 1,5-naphthalene diisocyanate or the like.
The polymeric diol used in the present invention include, for example, polymeric diol having no side chain such as polyester diol prepared from various straight-chain low monomeric diols and dicarboxylic acids such as adipic acid, phthalic acid, sebacic acid and dimeric acid; polycaprolactonediol; carbonates of various glycols; and polyether diols such as polytetromethylene glycol.
Examples of the polymeric diol having a methyl side chain in a molecule include polyester diol prepared from side-chain diol alone, such as 2-methyl-1,3-propanediol, 2-methyl-1,4-butanediol, 2-methyl-1,5-hexanediol, 3-methyl-1,5-hexanediol, neopenthyl glycol, 3-methyl-1,5-pentanediol and 2-methyl-1,8-octanediol, or a mixture with straight-chain diol, and dicarboxylic acids; polyvalerolactonediols made of xcex2-methyl-xcex4-valerolactone having a methyl side chain and the like. These compounds can be used alone or in combination with the above polymeric diols having no side chain. The number average molecular weight of these polymeric diols are within a range from 500 to 10,000, and preferably from 700 to 8,000.
The chain-extending agent used in the present invention includes, for example, a diol compound having a molecular weight of not more than 400. Specific compounds include ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanedilo, 1,9-nonanediol, bis-xcex2-hydroxyethoxybenzene and the like. There can also preferably be used side-chain diols such as 2-methyl-1,3-propanediol, 2-methyl-1,4-butanediol, 2-methyl-1,5-hexanediol, 3-methyl-1,5-hexanediol, neopenthyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, N-phenyldiisopropanolamine and the like. They can be used alone or in combination.
The thermoplastic polyurethane resin in the present invention is required to have a flow initiating temperature within a range from 80 to 150xc2x0 C. When the flow initiating temperature is less than 80xc2x0 C., it becomes difficult to prepare a nonwoven fabric by hot molding. On the other hand, when the flow initiating temperature excesses 150xc2x0 C., the flexibility of the nonwoven fabric is lost and the temperature on bonding rises to cause discoloration of the adherend so that it becomes unsuitable for use as an adhesive material for clothing.
As used herein, the term xe2x80x9cflow initiating temperaturexe2x80x9d refers to a temperature at which a resin initiates to melt and flow when heating at a constant heating rate. It is usually measured by, for example, a flow tester. The flow initiating temperature is an important physical property because it limits bonding conditions of a hot-melt nonwoven fabric adhesive material, especially heating temperature.
The hardness (JIS-A hardness) of the thermoplastic polyurethane resin of the present invention is required to be within a range from 65 to 98 degree. When the hardness is less than 65 degree, it becomes difficult to prepare a nonwoven fabric by heat molding. On the other hand, the hardness excesses 98 degree, the flexibility of the nonwoven fabric is lost so that it is not suited for used as an adhesive material for clothing.
By using, as at least one component of components of the thermoplastic polyurethane resin used in the present invention, a polymeric diol which has one or more methyl side chains, in particular has repeat units having a side chain in the molecule, it becomes possible to impart more excellent cold temperature flexibility, which is preferred. The cold temperature flexibility can be evaluated by a change between the hardness at normal temperature and that at cold temperature. A nonwoven fabric having excellent cold temperature flexibility is preferred because the pleasant feel to the touch is hardly deteriorated.
As the method preparing the thermoplastic polyurethane resin used in the present invention, for example, there can be employed any known methods of preparing the thermoplastic polyurethane resin, such as one shot method, prepolymer method, batch method, continuous method, extruder method, kneader method and the like. For example, according to the method using a kneader, a thermoplastic polyurethane resin in the form of flakes can be prepared by charging a polymeric diol and a chain-extending agent in a kneader, heating the mixture to 60xc2x0 C., charging an aliphatic diisocyanate, reacting the mixture for 10 to 60 minutes, and cooling the resultant. A block can be ground into flakes by using a grinder. These flakes are optionally formed into pellets by extruder.
Use of a catalyst on the preparation of the thermoplastic polyurethane resin of the present invention is not necessary, however, there can be used tertiary amines such as triethylamine and triethylenediamine; carboxylates of these tertiary amines; organometallic salts such as naphthenic acid metal salts (e.g., cobalt naphthenate and copper naphthenate, etc.), octenic acid metal salts, tin oleate, dibuthyltin dilaurate and tin octenate; and alkyl phosphines such as triethyl phasphine, tributyl phosphine and the like.
In the thermoplastic polyurethane resin used in the present invention, there can be suitably added inorganic waxes, organic waxes, protein powders and other processing aids; antioxidants, ultraviolet inhibitors, antistats, organic plasticizers and other thermoplastic resins improving formability of nonwoven fabric; and coloring materials and matting agents.
As the method of producing the nonwoven fabric of the present invention, for example, a conventionally known method can be employed.
For example, fibers obtained by melting with heating using an extruder, injecting through melt blown nozzles having orifices arranged in line at a constant pitch at a proper spanning temperature, blowing a heated air from an air slit thereby to make the spun yarn thin, were collected on a belt conveyer made of a wire, said belt conveyer running under the spun yarn, thus obtaining a nonwoven fabric wherein the fibers collected on the belt conveyer have been fused with their own heat.
To improve the flexibility of the nonwoven fabric, it is preferred to adjust the softness of the nonwoven fabric within a proper range. In case of the nonwoven fabric of the present invention, the softness Y (mm) and the weight of the nonwoven fabric X (g/m2) are preferably within the range which satisfies the expression: Yxe2x89xa60.2X+20.
Furthermore, the fiber diameter of the nonwoven fabric is preferably 100 xcexcm or less, more preferably 50 xcexcm or less, and particularly 30 xcexcm or less. The fiber diameter within the above range can maintain the proper flexibility, which is preferred.
A stretchable adhesive nonwoven fabric having a less softness can be obtained by using a thermoplastic polyurethane resin comprising an aliphatic diisocyanate, a polymeric diol and a chain-extending agent, at last one of which has one or more methyl side chain in the molecule. It can also be obtained by using a polymer having a low hardness (JIS-A hardness) of the thermoplastic polyurethane resin. However, when using a polymer having a low hardness, the release property from the conveyer belt is poor and it becomes impossible to stably produce even if the conveyer belt is coated with Teflon.
To improve the release property from the belt conveyer, the relationship between the melting temperature T and the melt viscosity V in the thermoplastic polyurethane resin used as a raw material may satisfy the following equation:
T=A log (V)+B
wherein T is a melting temperature (xc2x0C. ), V is a melt viscosity (poise), and A and B respectively satisfy the following equations:
xe2x88x9220xe2x89xa6Axe2x89xa6xe2x88x925,
100xe2x89xa6Bxe2x89xa6250.
Another method of improving the release property include a method of ejecting fibers through melt blown nozzles and promoting solidification with cooling by adjusting the distance between the melt blown nozzles and the conveyer belt to 15cm or more and adjusting the temperature of the heated air through the air slit to the same as or lower than the melting temperature of the thermoplastic polyurethane, unlike conventional melt blown production conditions.
The adherends can be bonded with each other by sandwiching the nonwoven fabric of the present invention between the adherends and heating at a suitable temperature. Therefore, the nonwoven fabric of the present invention is useful for bonding fiber products such as cloth and nonwoven fabric, a fiber product with a polymeric material, or polymeric materials with each other.
Furthermore, when the air permeability Z (cc/cm2/s) of the nonwoven fabric of the present invention and the weight X (g/m2) of the nonwoven fabric satisfy the expression: Zxe2x89xa75700xc3x9710xe2x88x920.019X, the air permeability of the laminate after bonding with the adherend is improved, which is preferred.
General uses of the nonwoven fabric of the present invention include, for example, bonding of a permeable film, bonding of various escutcheons and marks, and heat-bonding of a pattern formed on one side of the nonwoven fabric of the present invention using a general copying machine onto clothes such as T-shirt.
Furthermore, various uses utilizing the flexibility and air permeability as characteristics of the present invention are suggested. For example, when using the nonwoven fabric of the present invention as an adhesive material on lamination and of knitted fabrics having excellent stretchability (e.g. two-way tricot) with each other, the laminate can be obtained without impairing the stretchability and air permeability of the tricot. On the other hand, when using a material such as copolymerized PET as an adhesive material, the stretchability of the tricot is lost.
When using the nonwoven fabric of the present invention on lamination and bonding of a knitted fabric and a permeable film, the laminate utilizing both benefits can be obtained without impairing the stretchability and properties of the knitted fabric.
When using the nonwoven fabric of the present invention to bond a flock-finishing mark, there can be obtained a product which has hardly been provided with the flexibility, heretofore.
Heretofore, twists and sag often occurred during the use because the adhesive was applied in a form of dots. However, these problems can be completely solved by using the nonwoven fabric to bond parts of a belt of inner products.
According to the present invention, it becomes possible to obtain a supporting fabric and an interliner of clothes, which has satisfactory stretchability that has hardly obtained heretofore and are excellent in form retention, thus making it possible to produce a tie having excellent form retention.
Non-organic polymeric materials such as metal plate, glass, etc. and paper can also be heat-bonded, thus making it possible to obtain laminates wherein these materials are bonded with a cloth.